With the advent of increasingly complex and compact mechanical equipment, a need has developed for a wrench that may be utilized with such equipment. The wrench should be capable of engaging nuts or bolts located in confined spaces, i.e., a wrench head assembly having narrow lateral dimensions, and readily usable in confined spaces. At the same time, however, the wrench head assembly should have sufficient structural integrity for the application of high turning forces to the nut. The wrench should also be ratchetable. The wrench should also be capable of contacting the nut at more than two contact zones such that high torques may be more evenly distributed on the nut faces. Preferably, the wrench should be useable over a wide range of nut sizes.
Open-ended wrenches have greater utility in confined area applications as opposed to closed-ended wrenches such as box or socket type wrenches. Often it is extremely difficult, if not impossible, in confined area applications to provide the necessary transverse movement required by box or socket type wrenches to initially capture the nut. It will also be appreciated that box or socket type wrenches typically cannot be utilized on nuts associated with piping or tubing applications.
Adjustable wrenches are well known to those skilled in the art and to the laymen. An adjustable wrench has two contact zones and embodies certain features which may render it impractical for use in confined area applications. Most prior art adjustable wrenches utilize a manual adjustment mechanism such as a worm mechanism to open or close the jaws of the wrench In confined area applications, it may be awkward to activate the manual adjustment mechanism, it may be difficult to determine whether the worm mechanism is being properly activated, and it may be difficult to ascertain whether the wrench jaws have properly captured the nut.
In addition, open-ended adjustable wrenches apply torque to the nut at only two contact zones. Due to misadjustment or slippage between the nut faces and the wrench jaws, the moment arms of the torque applied to the nut may be reduced. The reduced moment arms necessitate the application of a higher turning force to ensure that a predetermined torque is applied to the nut. The increased turning force is often sufficient to cause damage to the nuts which reduces the moment arm even more. Damaging of nuts or operator injury are prime concerns in the use of adjustable wrenches, especially for applications involving plastic or nonferrous nuts or bolt heads. In addition, the application of higher turning forces requires thicker wrench head walls to withstand the higher torque forces, and thicker wrench head walls further limit the utility of adjustable wrenches in confined area applications.
Open-ended ratchet wrenches are also known to those skilled in the art and to the laymen, as exemplarily illustrated in U.S. Pat. No. 4,441,387. These wrenches are adjustable only in the sense that circular wrench discs of varying dimensions may be utilized to capture nuts or bolt heads of differing sizes. It will be appreciated, therefore, that these wrenches are limited inasmuch as the wrench must be removed from the work area to replace the circular wrench disc each time a nut of different size is to be torqued. Further, these ratchet wrenches are not self tightening. In addition, open-ended ratchet wrenches of this type are not immediately functional upon capture of the nut or bolt head by the circular wrench disc. Rather, a cam pin must be manually engaged prior to torqueing operation of the wrench. Manual engagement of the cam pin may be difficult in confined area applications. Additionally, these open-ended ratchet wrenches are relatively complex mechanically, thereby decreasing the reliability thereof and increasing the cost and time involved in fabrication and assemblage thereof.